Subsonic vs Supersonic Ammo

Video subsonic bullet speed

When it comes to ammunition, there are two basic types: subsonic and supersonic. Some cartridges are purely one or the other, and others offer a large variety based on powder selection and bullet types. We will look at both types to explain and explore the advantages and disadvantages of subsonic and supersonic ammunition.

What is Subsonic Ammo?

Mach 1 or the speed of sound is around 1100 feet per second or 761 miles per hour at sea level and ambient temperature. Anything traveling below that speed is considered a subsonic round. The way to check this, in case it is not indicated on the packaging, is to research the muzzle velocity of the round you wish to shoot. If the muzzle velocity is below 1100 feet per second, the round is subsonic.

Despite the lower muzzle velocity, this does not eliminate the need for ear protection. A subsonic round’s discharge and muzzle blast can damage your hearing, leading to hearing loss if ear protection is not used. Some rounds are subsonic by nature. Typically, these are cartridges that use a heavy and dense bullet like the 45-70 Government or 45 Colt. A few rounds can have a dual-purpose regarding loading parameters. Depending on the bullet used and of course the powder selection, these rounds may be loaded to subsonic or supersonic levels. At Grizzly Cartridge, we offer 45-70 +P and 45 Colt +P ammunition options, supersonic versions of the otherwise naturally subsonic ammo.

Advantages of Subsonic Ammo

Subsonic ammo has one primary advantage; it is particularly quiet when fired through a suppressor. This is because there is no sonic boom accompanying the fired subsonic load. This does not mean that the round is hearing safe without a suppressor. The noise of the fired round and the muzzle blast is present without that high powered supersonic crack familiar to high-powered rifle shooters. A secondary benefit to subsonic rounds is reduced felt recoil. A heavier bullet moving slower will not have the same felt recoil as a lighter bullet moving faster. This may be negligible or unnoticed on certain rounds, but it fully registers with the shooter when shooting a rifle round.

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Disadvantages of Subsonic Ammo

The downside of most subsonic ammunition is a limited effective range while hunting. For most hunting scenarios with subsonic loads, this is a moot point as those types of animals such as bear, deer and hogs are hunted at close range. This corresponds with such rounds used in close quarters combat, self-defense, and home-defense. Likewise, these types of shooting situations typically take place within ranges of 100 yards or less. In many cases, the subsonic speed will prevent reliable expansion with hollow point or expanding point ammunition. In others, the speed may affect the cycling of a semiautomatic firearm. There may not be enough gas to reliably cycle the action due to the loading. Apparently, the moral of the story is that a heavier bullet moving at subsonic speed is not as effective at long range.

What is Supersonic Ammo?

When a projectile breaks the sound barrier and goes above 1100, it is supersonic. This is the most common type of ammunition available and the only type most people have ever shot. Most supersonic ammunition comes in the form of bottlenecked rifle cartridges such as the 308 Winchester and 300 Winchester Magnum. Yet, there are a few straight wall cartridges that Supersonic rounds such as these are known for. Their higher velocity and loud sonic boom are from breaking the sound barrier.

Supersonic ammunition exists in the world of handgun cartridges as well. Rounds such as 9mm, 10mm, and all of the big revolver cartridges travel at supersonic speeds. Rounds travel at supersonic speeds particularly when using jacketed ammunition and firing through a longer barrel or a pistol caliber carbine without a short barrel. Also be aware, rounds that are traditionally a subsonic round can be loaded to supersonic levels as a +P round when using a lighter 185-grain bullet.

However, even if ammunition is branded as subsonic or has a subsonic muzzle velocity, it may turn into supersonic ammunition in certain types of firearms. Barrel length can have an impact on certain types of subsonic ammunition and will transform the ballistics to transonic or supersonic levels if the longer barrel increases the muzzle velocity above 1130 fps.

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Advantages of Supersonic Ammo

Most rifle ammunition available is supersonic. Everything from 22 long rifle to 50 BMG will break the sound barrier when fired, and many handgun cartridges from 9mm, 10mm, and the Magnum handgun calibers travel at supersonic speeds. Certain types of subsonic ammunition can surpass the speed of sound based on barrel length, too. As mentioned previously, as a projectile moves down a barrel, it will pick up velocity in many cases. If a round is transonic or barely subsonic, it can very well become supersonic if it was intended for a 6” to 10” barrel, and it is being fired through a 16” to 20” barrel.

Supersonic ammunition excels for the most part as a long-range hunting or target round. The increased muzzle velocity and terminal ballistics increases the effective range over the subsonic variants. This is true in handgun rounds loaded to +P levels. The increased pressure (indicated by the +P designation) usually brings increased velocity to the table.

Disadvantages of Supersonic Ammo

The primary disadvantage of supersonic ammunition is that it is difficult to suppress when shooting with a silencer. Although suppressor effectiveness is constantly improving and much of the loudest supersonic rounds can be muffled, the sonic boom will always prevent true suppression. Even when shooting with a suppressor, a supersonic round will require ear protection in addition to the silencer mounted on the barrel to be truly hearing safe. It may seem unusual, but it can be the case. This highlights the importance to check the rating for the silencer’s decibel reduction and velocity of the ammunition.

Which is Better: Subsonic vs Supersonic Ammo

As to which type of ammunition is better, that depends on your needs for shooting. Sometimes you need the lower velocity of a subsonic round, especially if you are a fan of 45-caliber bullets. Other instances might require a higher velocity round with a flatter bullet trajectory for long range shooting. 300 Blackout ammomay be the most versatile as a rifle or pistol cartridge in the AR-15 platform. Whether using factory or hand-loaded 300 Blackout ammo, the shooter can choose anything from a heavy slow-moving bullet for use in a suppressor or a high velocity hunting round with longer range in the same firearm. In fact, most 300 Blackout subsonic rounds can be fired through a pistol silencer rated for a pistol caliber such as 9mm. The supersonic rounds, however, would need to use a dedicated .30-caliber rifle suppressor.

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If you are ever unsure of whether a round is supersonic or subsonic, you can verify the bullet’s velocity using a chronograph at the range.

Choose the Right Ammunition No Matter Your Preference

In many cases, the choice of subsonic vs supersonic ammunition will depend on whether the shooter is using a suppressor. The sound difference to the human ear between a 9mm supersonic round using a 115-grain bullet vs. a subsonic round loaded with a 147-grain bullet or heavier will be for the most part, unnoticeable. Yet, using a suppressor and hearing the comparison with and without that subsonic crack will make the difference very evident. If a suppressor is taken out of the equation, it comes down to the individual needs of the shooter. If a heavy, slower moving bullet with a flat trajectory is required, then the shooter can go the subsonic route. Should the requirements be a long-range cartridge with higher velocity and more energy delivered to the target, the choice will clearly be a supersonic cartridge. In the case of handgun cartridges for home defense or self-defense, there are two schools of thought: a heavier slower moving bullet that lowers magazine capacity due to the size of the round (subsonic) or a lighter faster moving bullet with increased magazine capacity (supersonic). As a shooter, you will tend to have a preference of one type over the other for different situations. What’s important is choosing the right ammunition for yourself and your firearm to have a safe shooting experience. For all your ammunition needs, shop Grizzly Cartridge with second-to-none quality.

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Ethan Smith is a seasoned marine veteran, professional blogger, witty and edgy writer, and an avid hunter. He spent a great deal of his childhood years around the Apache-Sitgreaves National Forest in Arizona. Watching active hunters practise their craft initiated him into the world of hunting and rubrics of outdoor life. He also honed his writing skills by sharing his outdoor experiences with fellow schoolmates through their high school’s magazine. Further along the way, the US Marine Corps got wind of his excellent combination of skills and sought to put them into good use by employing him as a combat correspondent. He now shares his income from this prestigious job with his wife and one kid. Read more >>